It is not difficult to imagine the creation of some sort of a criminal tribunal that could, in theory, prosecute political leaders who resorted to war against Ukraine. The international crime of aggression is fit for purpose. It is the institutional mechanism that awaits. As diplomats discuss the prospect of different models of an aggression tribunal, a first step could be taken most immediately: the establishment of an “interim prosecutor’s office” in The Hague.

The idea is reflected in a proposal by Ukraine and The Netherlands. It has much to offer. Such an office would have the potential to preserve evidence that could be essential to future prosecutions and create buy-in from States that may otherwise be concerned about establishing another expensive international court with uncertain outcomes.

I communicated with current and former diplomats from the United States and Ukraine, among others, for this article.

In early November, Ukrainian officials announced a diplomatic effort to create an Interim Prosecutor’s Office (IPO), and later that month the Prosecutor General of Ukraine Andriy Kostin spoke about the project. By the end of the month, the Netherlands proposed the establishment of such an office in The Hague in a manner that dovetailed with the European Commission’s announcement of its effort to help establish a criminal tribunal on aggression. Former Prime Minister Gordon Brown aptly described these political developments as a “breakthrough.”

An IPO comes with certain advantages. Rather than await a full-blown international court with full-time judicial and administrative staff and buildings to house them, prosecutors and investigators could carry out time-sensitive work. Alex Whiting, who currently serves as the acting Specialist Prosecutor of the Kosovo Specialist Prosecutor’s Office in The Hague, told me that this could include collecting, preserving, organizing, and assessing evidence, as well as anticipating and analyzing legal issues as part of the detailed legal work necessary to ground any criminal charges. The IPO would look to collect open-source evidence as well as evidence from Ukrainian sources, other governments, international organizations, civil society, and experts on Russian and Belarusian political and military structures. Given that aggression is a leadership crime, the IPO could identify whom within Putin‘s circle should be held criminally responsible for planning, preparing, or executing Russia’s acts of aggression. Because allowing a State’s territory to be used by another State for perpetrating an act of aggression may also be prosecutable, the IPO could also consider the responsibility of senior Belarusian leaders.

The IPO’s work product could show States what a return on their investment in a future dedicated tribunal could yield. A sort of concept of proof: demonstrating whether the investigation of the crime of aggression can be done efficiently and in harmony with prosecutions of war crimes and other atrocities by the International Criminal Court. For more on the latter, I highly recommend Ambassador (ret.) David Scheffer’s article in Just Security, “Forging a Cooperative Relationship Between International Criminal Court and a Special Tribunal for Aggression Against Ukraine” (English version) (Ukrainian version).

Another leading expert and former senior war crimes prosecutor, Ambassador (ret.) Stephen Rapp said in an email, “There is more to do than many appreciate. The prosecution must be able to prove not only that specific Russian leaders are responsible for defined ‘acts of aggression’ but also that the acts were of sufficient ‘character, gravity, and scale’ as to constitute the ‘crime of aggression.’”

That work will redound to the benefit of other international initiatives for accountability, Rapp further wrote. “The evidence they gather on the character of the acts can also be of value in ICC trials on war crimes and crimes against humanity.  As to gravity and scale, their information could be useful in later processes to compensate for all the harms caused by the aggression.” That observation has relevance for the Claims Commission sought by Ukraine as well as related international efforts.

An important design feature for the IPO would be to include international staffing at all levels – to help ensure the independence and impartiality of the prosecutorial team and also bring expertise in international investigations and prosecutions.

That raises the question whether the prosecutors could carry out all their work without judicial oversight. David Schwendiman, who served as Chief Prosecutor of the Kosovo Specialist Prosecutor’s Office in The Hague from 2016 to 2018, said in an email, “It must be made clear from the beginning that a special investigative task force operating without a court or tribunal and without rules established by the court or tribunal, is not able to make traditional prosecution decisions about who to charge or what to charge. It is a common assumption made by people with little or no experience with the functioning of a criminal justice system, especially when it comes to investigating or prosecuting complex crimes.”

Those creating an IPO could study and borrow from features of the Kosovo Specialist Chambers and Specialist Prosecutor’s Office, which is also seated in The Hague. It has relied on a roster of judges that is activated only when there is judicial work to be done, that way avoiding judges being paid to sit in The Netherlands with little to do. The slimmed-down Kosovo model is a relatively small court and prosecution office – a good template for what’s needed here.

An IPO for the crime of aggression against Ukraine could be a relatively small operation. The investigation and prosecution of aggression against Ukraine will be relatively straightforward in comparison to investigations of myriad war crimes committed during the heat of battle. Whiting, who has experience at three different international tribunals, told me that a small number of prosecutors, investigators, and analysts would be sufficient to staff the office. The aggression against Ukraine is overt, and there is no question about the commanding role of senior leaders, however that group is ultimately defined. That’s amply demonstrated by two “model indictments” – one produced by Professor Rebecca Hamilton and me and another produced by Open Society Justice Initiative’s executive director James A. Goldston – which were based simply on open source information.

Goldston said in an email, “The establishment of an interim prosecution office for the crime of aggression in Ukraine seems a well-intended, if modest, step forward that nonetheless leaves much to be done if the Russian leadership is to be held accountable for its actions. Dutch government sponsorship and the participation of prosecutors from Ukraine and other countries are welcome signs of commitment. But the fundamental task remains of building broad-based political support for an aggression tribunal with the necessary legal foundation and legitimacy.”

Ambassador Rapp wrote, “Establishing an interim prosecution office will build momentum for creation of an aggression tribunal and will provide such a tribunal with a head start in gathering evidence and framing indictments.”

While the prosecutorial work may be relatively straightforward, what goes into ensuring that such an office has sustainable financial, political, and legal footing may require deft diplomatic efforts. Schwendiman advised:

“Problems are neither a reason nor an excuse for not trying to come up with a workable mechanism for holding people accountable for the crime of aggression in Ukraine, but more thought needs to be given to the practical problems involved. It is essential that those with practical experience with the fundamentals of creating and running a prosecution office – and a court or tribunal – are consulted and listened to. Practitioners of the art of acquiring and keeping staff, of keeping an office funded, of setting and enforcing policy for the office that will ensure whatever it does will be done according to acceptable international and local standards, that what it does will likely meet any standard imposed by a tribunal if one is eventually set up, of creating and maintaining the political conditions that will ensure the independence of the office as well as meeting the administrative needs of staff.”

A chief prosecutor may need to hit the ground running to establish cooperation with States and other organizations to address the issues Schwendiman outlined.

Schwendiman also pointed to questions of legal authority that may need to be answered under certain circumstances: “How will that authority be enforced if it comes to exercising the functions of the prosecutor in the case of recalcitrant witnesses or states or organizations in possession of information the prosecutor must have to do her job? Where does the prosecutor go to get authorization to search or to access sensitive information or use extraordinary measures to acquire usable evidence?”

A final question for any ultimate court will be whether it can try cases in absentia. Most European legal systems, including in Ukraine and The Netherlands, allow for this approach. Trials in absentia are based on the theory that defendants’ have the right but not the obligation to be present. A long, expensive in absentia trial would likely not find support among States. However, an efficient process might find more political backing. The Dutch handling of the MH-17 trial in absentia is a good example and widely considered effective.

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One set of ideas draws broad support: Aggression in the case of Ukraine must not go unanswered. International criminal norms must be enforced. The international legal system currently lacks an institutional mechanism to accomplish such goals.

An interim prosecutor’s office in The Hague, learning from both mistakes and successes of the past, may offer an important first step.

IMAGE: Dutch Minister of Foreign Affairs Wopke Hoekstra gives an opening speech at the Ukraine Accountability Conference, hosted by the Government of the Netherlands, the Office of the Prosecutor of the International Criminal Court, and the European Commission at ministerial level on July 14, 2022. (Dutch Ministry of Foreign Affairs)